A process for the rectification of NMP

Abstract

This invention belongs to the field of NMP production technology, specifically involving an NMP distillation process, including the following steps: (1) feeding the crude NMP product sequentially into a deammoniation tower, a dehydration tower, and a finished product tower for processing, finally obtaining NMP heavy components and NMP finished product; (2) feeding the NMP heavy components into a flash distillation tower, the bottom of which is equipped with a cooler and a buffer tank; the bottom heavy component material generated during the operation of the flash distillation tower is fed into the cooler for cooling, so that the bottom heavy component material is cooled to near room temperature; (3) drawing negative pressure at the top of the buffer tank, the cooled bottom heavy component material enters the buffer tank; when the liquid level in the buffer tank reaches 75-85%, the feeding of bottom heavy component material into the buffer tank is stopped, and then nitrogen gas is introduced into the buffer tank to gradually increase the pressure in the buffer tank, and the bottom heavy component material in the buffer tank is discharged. This scheme can change the NMP heavy component processing from intermittent operation to continuous operation, effectively improving the distillation efficiency of NMP.

Description

Technical Field

[0001] This invention belongs to the field of NMP production technology, specifically relating to an NMP distillation process. Background Technology

[0002] NMP (N-methylpyrrolidone) is a highly selective and stable polar solvent, making it an excellent cleaning agent for high-precision electronics, circuit boards, and lithium batteries, with wide applications across various industries. The production of NMP involves two processes: synthesis and distillation. The specific process route is as follows: first, ammonialation of purified GBL intermediate with monomethylamine is used to produce crude NMP; then, the crude NMP is refined and distilled to obtain the final NMP product. The process flow diagram for the refining and distillation of crude NMP is shown below. Figure 1 As shown, in Figure 1 In conventional processes, the flash distillation tower operates intermittently. Heavy NMP components are fed into the flash distillation tower for negative pressure distillation, heated with heat transfer oil, maintaining a vacuum greater than -95 kPaG, a top temperature of 120°C, and a bottom temperature of 180°C. The distillate from the top is returned to the synthesis unit for reuse, while the heavy components from the bottom are discharged directly as hazardous waste after cooling. Due to the high temperature and negative pressure at the bottom of the flash distillation tower, the tower must be stopped each time hazardous waste is discharged. The bottom material must be cooled to near room temperature and then purged with nitrogen to adjust the pressure to a slightly positive pressure before direct discharge. This cooling process takes approximately 48 hours, severely impacting the flash distillation tower's processing capacity and resulting in low NMP distillation efficiency. Summary of the Invention

[0003] The present invention aims to provide an NMP distillation process to solve the problem of low NMP distillation efficiency caused by the inability of flash distillation columns to operate continuously.

[0004] To achieve the above objectives, the present invention provides an NMP distillation process comprising the following steps:

[0005] (1) The crude NMP product is fed into the deammoniation tower for deammoniation treatment. After the deammoniation treatment is completed, it is fed into the de-heavy tower for further processing to obtain NMP heavy components and NMP primary product. The NMP primary product is fed into the dehydration tower for dehydration treatment. After the dehydration treatment is completed, it is fed into the product tower for further processing to obtain NMP heavy components and NMP product.

[0006] (2) The NMP heavy components are fed into the flash tower for processing. The bottom of the flash tower is equipped with a cooler and a buffer tank connected to the cooler. The heavy components generated in the bottom of the flash tower during operation are fed into the cooler for cooling, so that the heavy components in the bottom of the tower are cooled to near room temperature.

[0007] (3) The top of the buffer tank is drawn into negative pressure, and the cooled bottom heavy component material enters the buffer tank; when the liquid level in the buffer tank reaches 75-85%, stop feeding the bottom heavy component material into the buffer tank, and then introduce nitrogen into the buffer tank to gradually increase the pressure in the buffer tank and discharge the bottom heavy component material in the buffer tank.

[0008] The working principle and beneficial effects of this scheme are as follows: By adding a cooler and a buffer tank to the bottom of the flash distillation tower, the heavy components generated during the operation of the flash distillation tower are sent to the cooler for cooling before being discharged into the buffer tank, and finally, hazardous waste is collected in the buffer tank. This method eliminates the need to specifically stop the flash distillation tower to discharge the heavy components from the bottom, thus increasing the processing capacity of the flash distillation tower. It allows NMP heavy component processing to be changed from intermittent operation to continuous operation, reduces manual operation, and effectively improves the distillation efficiency of NMP.

[0009] Optionally, when the material level in the buffer tank reaches 80%, the feeding of heavy component material from the bottom of the tower into the buffer tank is stopped, and then nitrogen gas is introduced into the buffer tank to discharge the heavy component material from the bottom of the tower.

[0010] Optionally, the cooler is a shell-and-tube heat exchanger.

[0011] Optionally, the cooler includes a shell and multiple heat pipes. The shell contains a heat insulation plate that divides it into an upper and lower chamber. The heat pipes are fixed to the heat insulation plate, with the evaporation section of the heat pipes located in the lower chamber and the condensation section located in the upper chamber. A feed pipe and a discharge pipe, both communicating with the lower chamber, are connected to the shell. A cooling section is located in the upper chamber to reduce the temperature of the condensation section of the heat pipes. When the cooler needs to operate, the cooling section is operated first to cool the condensation section of the heat pipes. The heavy components generated during the operation of the flash evaporator are fed into the lower chamber through the feed pipe, cooled there, and then discharged through the discharge pipe. In the lower chamber, the heavy components come into contact with the evaporation section of the heat pipes. The working fluid in the evaporation section absorbs the heavy components from the bottom of the flash evaporator, causing them to evaporate and vaporize. The resulting steam reaches the condensation section of the heat pipes under the influence of temperature and pressure differences. In the condensation section, steam condenses and liquefies upon encountering cold surfaces. The resulting liquid returns to the evaporation section of the heat pipe under gravity, and this cycle repeats continuously, transferring heat from the heavy components in the bottom of the tower to the upper chamber, thus achieving the purpose of cooling the heavy components in the bottom of the tower. The cooler using this design offers excellent cooling performance and high efficiency, rapidly reducing the temperature of the heavy components in the bottom of the tower, allowing them to be promptly discharged into the buffer tank without affecting the normal operation of the flash tower.

[0012] Optionally, the cooling section is located above the heat pipe condensation section; the cooling section includes a water inlet pipe, an air inlet pipe, a bracket fixed to the upper cavity, a rotating shaft rotatably connected to the bracket, and multiple blades located at the lower part of the rotating shaft, with nozzles on the blades; the nozzles have a mixing chamber, an air inlet channel, a water inlet channel, and a nozzle, all of which are connected to the mixing chamber; the rotating shaft has a cavity and an annular inner cavity surrounding the cavity, and an air inlet connected to the annular inner cavity; multiple rotating blades are located in the cavity, one end of the water inlet pipe is connected to the cavity, and the water sprayed from the water inlet pipe can drive the rotating shaft to rotate through the rotating blades; a water pipe connected to the cavity is connected to the rotating shaft, and the water pipe is connected to the water inlet channel; an annular sleeve that rotates and is sealed to the rotating shaft is fixed on the bracket, and an annular cavity connected to the air inlet is located inside the annular sleeve; one end of the air inlet pipe is connected to the annular cavity; a vent pipe connected to the annular cavity is connected to the rotating shaft, and the vent pipe is connected to the air inlet channel.

[0013] When the cooler needs to operate, a water pump or similar device supplies cooling water into the inlet pipe. The cooling water flows along the inlet pipe into the cavity, where it sprays onto the rotating blades, causing them to rotate and thus driving the rotating shaft. The blades and nozzles on the blades also move accordingly. The cooling water in the cavity flows sequentially through the water pipe and the inlet channel, finally entering the mixing chamber. Simultaneously, an air compressor or similar device supplies air into the intake pipe. The air flows sequentially through the annular cavity, the air inlet, the vent pipe, and the intake channel, finally entering the mixing chamber. Cooling water enters the mixing chamber through the inlet channel, and air enters through the intake channel. The air and cooling water collide violently in the mixing chamber, causing the cooling water to form a mist that is sprayed out from the nozzle. This mist of cooling water falls onto the condenser section of the heat pipe, cooling it down. In this design, the cooler provides multiple cooling effects on the condenser section of the heat pipe, resulting in excellent cooling performance. First, the cooling water falls directly onto the condenser section of the heat pipe, effectively cooling it. Secondly, the cooling water mist cools the condenser section of the heat pipe. This mist evaporates easily, absorbing heat during the evaporation process, further reducing the temperature of the condenser section. Then, the blades rotate during cooler operation, accelerating airflow and facilitating heat dissipation from the condenser section. Finally, the nozzles rotate with the blades, spraying cooling water mist that falls from all directions, ensuring good contact between the cooling water and the condenser section of each heat pipe, guaranteeing uniform cooling. Furthermore, the rotating nozzles impart centrifugal force to the cooling water mist, accelerating its descent and ensuring cooling efficiency.

[0014] Optionally, the condenser section of the heat pipe is provided with multiple fins. The fins help accelerate heat dissipation from the condenser section, allowing the heat pipe to operate more efficiently.

[0015] Optionally, the air intake channel and the water intake channel are perpendicular to each other. This arrangement ensures that the gas entering through the air intake channel and the water entering through the water intake channel collide violently, allowing the water to be well atomized. Attached Figure Description

[0016] Figure 1 This is a production flow diagram of the refining and distillation of crude NMP products in the background technology;

[0017] Figure 2 This is a schematic diagram of the flash evaporator in operation according to Embodiment 1 of the present invention;

[0018] Figure 3 This is a schematic diagram of the cooler structure in Embodiment 2 of the present invention;

[0019] Figure 4 for Figure 3 Enlarged view of section A. Detailed Implementation

[0020] The following detailed description illustrates the specific implementation method:

[0021] The reference numerals in the accompanying drawings include: flash tower 10, shell and tube heat exchanger 11, buffer tank 12, shell 20, heat insulation plate 21, lower cavity 22, upper cavity 23, feed pipe 24, discharge pipe 25, heat pipe 30, fins 31, rotating shaft 40, cavity 41, annular inner cavity 42, rotating blade 43, sealing head 44, air inlet 45, air inlet pipe 50, water inlet pipe 51, support 60, annular sleeve 61, annular cavity 62, blade 70, vent pipe 71, water inlet pipe 72, nozzle 80, mixing chamber 81, air inlet channel 82, water inlet channel 83, and nozzle 84.

[0022] Example 1

[0023] An NMP distillation process includes the following steps:

[0024] (1) The crude NMP product is fed into the deammoniation tower for deammoniation treatment. After the deammoniation treatment is completed, it is fed into the heavy component deammoniation tower for further processing to obtain NMP heavy components and NMP primary product. The NMP primary product is fed into the dehydration tower for dehydration treatment. After the dehydration treatment is completed, it is fed into the product tower for further processing to obtain NMP heavy components and NMP product.

[0025] (2) The NMP-recombined fraction is sent to flash tower 10 for processing (e.g. Figure 2 As shown, the reboiler of the flash distillation tower 10 is equipped with a cooler and a buffer tank 12. In this embodiment, the cooler is a shell-and-tube heat exchanger 11. The buffer tank 12 is connected to the cooler, and the material in the cooler can be fed into the buffer tank 12. The heavy component material generated in the reboiler during the operation of the flash distillation tower 10 is sent to the cooler for cooling, so that the heavy component material in the reboiler is cooled to near room temperature.

[0026] (3) A negative pressure is drawn at the top of the buffer tank 12, and the cooled heavy component material from the bottom of the tower will enter the buffer tank 12. When the liquid level in the buffer tank 12 reaches 75-85% (in this embodiment, the liquid level in the buffer tank 12 reaches 80%), the feeding of the heavy component material from the bottom of the tower into the buffer tank 12 is stopped, and then nitrogen gas is introduced into the buffer tank 12 to gradually increase the pressure inside the buffer tank 12, thereby discharging the heavy component material from the bottom of the tower into the buffer tank 12.

[0027] Example 2

[0028] The difference between this embodiment and Embodiment 1 is that the cooler used in this embodiment is different from that in Embodiment 1, such as... Figure 3 , Figure 4 As shown, in this embodiment, the cooler includes a shell 20 and multiple heat pipes 30 (in this embodiment, the heat pipes 30 are gravity-type heat pipes 30). A heat insulation plate 21 is welded inside the shell 20, dividing the shell 20 into an upper cavity 23 and a lower cavity 22. The heat pipes 30 are fixed to the heat insulation plate 21. The evaporation section of the heat pipes 30 is located in the lower cavity 22, while the condensation section of the heat pipes 30 is located in the upper cavity 23. Multiple fins 31 are welded to the condensation section of the heat pipes 30 to facilitate heat dissipation. A feed pipe 24 and a discharge pipe 25 are connected to the shell 20. Both the feed pipe 24 and the discharge pipe 25 communicate with the lower cavity 22. The heavy component material generated in the reboiler during the operation of the flash evaporator 10 is fed into the lower cavity 22 through the feed pipe 24 and then discharged through the discharge pipe 25. The housing 20 is also connected to a drain pipe (not shown in the figure) that communicates with the upper cavity 23. When it is necessary to drain the liquid in the upper cavity 23, it can be drained through the drain pipe.

[0029] The upper cavity 23 is equipped with a cooling section for reducing the temperature of the condensing section of the heat pipe 30. The cooling section is located above the condensing section of the heat pipe 30. One cooling section can be provided, or two or more can be provided depending on the actual situation. The cooling section includes a water inlet pipe 51, an air inlet pipe 50, a support 60, a rotating shaft 40, and multiple blades 70 (in this embodiment, four blades are provided). The support 60 is welded to the inner wall of the upper cavity 23, and the rotating shaft 40 is rotatably connected to the support 60 via bearings. The blades 70 are welded to the lower part of the rotating shaft 40, and nozzles 80 are fixedly mounted on the blades 70. The nozzle 80 has a mixing chamber 81, an air inlet channel 82, a water inlet channel 83, and a nozzle 84. The nozzle 84, air inlet channel 82, and water inlet channel 83 are all connected to the mixing chamber 81. The air inlet channel 82 and the water inlet channel 83 are perpendicular to each other. This arrangement ensures that the gas entering through the air inlet channel 82 and the water entering through the water inlet channel 83 collide violently, allowing the water to be well atomized.

[0030] The rotating shaft 40 has a cavity 41 and an annular inner cavity 42 surrounding the cavity 41. Multiple air inlets 45 communicating with the annular inner cavity 42 are located on the rotating shaft 40. Multiple rotating blades 43 are welded to the inner wall of the cavity 41. One end of the water inlet pipe 51 is connected to the cavity 41. Specifically, a sealing head 44 is sealed at the upper end of the rotating shaft 40, rotating and sealingly connected to the inner wall of the rotating shaft 40. One end of the water inlet pipe 51 passes through the sealing head 44 and communicates with the cavity 41. Water sprayed from the water inlet pipe 51 can be sprayed onto the rotating blades 43, causing the blades 43 to rotate and thus driving the rotating shaft 40 to move together.

[0031] A water pipe 72 communicating with the cavity 41 is fixedly connected to the rotating shaft 40, and the other end of the water pipe 72 is connected to the water inlet channel 83 of the nozzle 80. An annular sleeve 61 is welded onto the bracket 60, and the annular sleeve 61 rotates and is sealed to the rotating shaft 40. An annular cavity 62 communicating with the air inlet 45 is opened inside the annular tube; one end of the air inlet pipe 50 is fixed to the annular sleeve 61 and communicates with the annular cavity 62. A vent pipe 71 communicating with the annular cavity 62 is fixedly connected to the rotating shaft 40, and the other end of the vent pipe 71 is connected to the air inlet channel 82 of the nozzle 80.

[0032] When the cooler needs to operate, first operate the cooling section to cool the condenser section of the heat pipe 30. The specific process is as follows: Cooling water is introduced into the inlet pipe 51 using a water pump or other equipment. The cooling water enters the cavity 41 along the inlet pipe 51 and is sprayed onto the rotating blades 43, causing the blades 43 to rotate. This, in turn, drives the rotating shaft 40 to move, and the blades 70 and the nozzles 80 on the blades 70 also move accordingly. The cooling water in the cavity 41 flows sequentially through the water pipe 72 and the inlet channel 83, finally entering the mixing chamber 81. At the same time, air is introduced into the air inlet pipe 50 using an air compressor or other equipment. The air flows sequentially through the annular cavity 62, the air inlet 45, the air pipe 71, and the air inlet channel 82, finally entering the mixing chamber 81. Cooling water enters the mixing chamber 81 through the water inlet channel 83, and air enters the mixing chamber 81 through the air inlet channel 82. The air and cooling water collide violently in the mixing chamber 81, causing the cooling water to form a mist and be sprayed out from the nozzle 84. The mist of cooling water falls on the condensation section of the heat pipe 30 to cool it down.

[0033] The heavy component material generated during the operation of the flash evaporator 10 is fed into the lower chamber 22 through the feed pipe 24. After being cooled in the lower chamber 22, it is discharged through the discharge pipe 25. While in the lower chamber 22, the heavy component material comes into contact with the evaporation section of the heat pipe 30. The working fluid in the evaporation section of the heat pipe 30 absorbs the vaporization of the heavy component material, and the resulting steam reaches the condensation section of the heat pipe 30 under the influence of temperature and pressure differences. The steam condenses and liquefies upon encountering the cold surface in the condensation section, and the resulting liquid returns to the evaporation section of the heat pipe 30 under gravity. This cycle repeats continuously, allowing the heat from the heavy component material in the bottom chamber to be continuously transferred to the upper chamber 23, thus achieving the purpose of cooling the heavy component material in the bottom chamber.

[0034] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics in the solutions is not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or its practicality.

Claims

1. An NMP distillation process, characterized in that: Includes the following steps: (1) The crude NMP product is fed into the deammoniation tower for deammoniation treatment. After the deammoniation treatment is completed, it is fed into the de-heavy tower for further processing to obtain NMP heavy components and NMP primary product. The NMP primary product is fed into the dehydration tower for dehydration treatment. After the dehydration treatment is completed, it is fed into the product tower for further processing to obtain NMP heavy components and NMP product. (2) The NMP heavy components are fed into the flash tower for processing. The bottom of the flash tower is equipped with a cooler and a buffer tank connected to the cooler. The heavy components generated in the bottom of the flash tower during operation are fed into the cooler for cooling, so that the heavy components in the bottom of the tower are cooled to near room temperature. (3) A negative pressure is drawn from the top of the buffer tank, and the cooled reboiler heavy components enter the buffer tank; when the liquid level in the buffer tank reaches 75... When the pressure reaches 85%, stop feeding the heavy component material from the bottom of the tower into the buffer tank, and then introduce nitrogen into the buffer tank to gradually increase the pressure inside the buffer tank, thereby discharging the heavy component material from the bottom of the tower into the buffer tank. The cooler includes a shell and multiple heat pipes. The shell is equipped with a heat insulation plate that divides the shell into an upper cavity and a lower cavity. The heat pipes are fixed on the heat insulation plate. The evaporation section of the heat pipes is located in the lower cavity, and the condensation section of the heat pipes is located in the upper cavity. The shell is connected to an inlet pipe and an outlet pipe, both of which are connected to the lower cavity. The upper cavity is equipped with a cooling section for reducing the temperature of the condensation section of the heat pipes. The cooling section is located above the heat pipe condensation section. The cooling section includes a water inlet pipe, an air inlet pipe, a bracket fixed to the upper cavity, a rotating shaft rotatably connected to the bracket, and multiple blades located at the lower part of the rotating shaft. Each blade has a nozzle. The nozzle contains a mixing chamber, an air inlet channel, a water inlet channel, and a nozzle. The nozzle, air inlet channel, and water inlet channel are all connected to the mixing chamber. The rotating shaft contains a cavity and an annular inner cavity surrounding the cavity. An air inlet is located on the rotating shaft and communicates with the annular inner cavity. Multiple rotating blades are located within the cavity. One end of the water inlet pipe communicates with the cavity, and the water sprayed from the water inlet pipe drives the rotating shaft to rotate via the rotating blades. A water pipe connected to the cavity is connected to the rotating shaft and is connected to the water inlet channel. An annular sleeve, which rotates and is sealed to the rotating shaft, is fixed to the bracket. An annular cavity, which communicates with the air inlet, is located within the annular sleeve. One end of the air inlet pipe communicates with the annular cavity. A vent pipe connected to the annular cavity is connected to the rotating shaft and communicates with the air inlet channel.

2. The NMP distillation process according to claim 1, characterized in that: When the liquid level in the buffer tank reaches 80%, stop feeding the heavy component material from the bottom of the tower into the buffer tank, and then introduce nitrogen gas into the buffer tank to discharge the heavy component material from the bottom of the tower.

3. The NMP distillation process according to claim 2, characterized in that: The cooler is a shell-and-tube heat exchanger.

4. The NMP distillation process according to claim 1, characterized in that: The condenser section of the heat pipe has multiple fins.

5. The NMP distillation process according to claim 4, characterized in that: The air intake channel and the water intake channel are perpendicular to each other.

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